Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades are the primary elements for converting wind energy into electrical energy. The blades have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between the sides. Consequently, a lift force, which is directed from a pressure side towards a suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is geared to the generator for producing electricity.
The rotor blades typically consist of a suction side shell and a pressure side shell that are bonded together at bond lines along the leading and trailing edges of the blade. An internal shear web extends between the pressure and suction side shell members and is bonded to spar caps affixed to the inner faces of the shell members. Relatively exact length dimensions are required for the shear web to span between the spar caps and achieve a bond between the spar caps and shear web having sufficient width and thickness dimensions. Achieving these dimensions, as well as an adequate bond, can be difficult and the juncture between the spar caps and shear web is a time-consuming and tedious process that often requires significant re-work.
With typical blade configurations, the shear web is a continuous member that spans between the spar caps, and a rigid flange is used to achieve a desired bond width for bond paste applied between the spar caps and transverse ends of the shear web. This configuration, however, places significant stresses at the juncture between the shear web and spar cap and often results in the use of excess bond paste to achieve a desired bond width at this critical juncture. The excess paste contributes unnecessary weight to the blade and can break off and result in blade “rattling” during operation of the wind turbine (a not uncommon complaint from wind turbine owners/operators). Also, air voids and unpredictable squeeze-out of the bond paste in the typical configurations can result in areas of decreased bond strength, which is particularly problematic in sections of the blade where repair is not possible from within the rotor blade.
Accordingly, the industry would benefit from an improved bond configuration between the shear web and spar caps that addresses one or more of the deficiencies of certain conventional configurations.